The objective of the proposed research is to study the causes and effects of population change in the preindustrial setting, and the possible existence, characteristics, and operation of mechanisms regulating population size and hence economic welfare within the preindustrial economic-demographic system. The specific topics investigated include the following: population and real wages; surplus labor; natural fertility; mortality and wages; population cycles; climate and demographic change; the Heer-O'Hara effect; demand for labor versus mortality as prime mover in demographic history. The basic methodology is model-oriented and econometric. Models are developed expressing contrasting hypotheses, and are estimated and tested using simultaneous equation regression methods and cross-spectral analysis. A unique set of data is available for the analysis. The Cambridge Group for the History of Population and Social Structure has collected monthly totals of baptisms, burials and marriages for 404 English parishes, 1538 to 1840. These new data will be used to develop measures of population, fertility and mortality for England over the three-century period.